Best cochlear locations for delivering interaural timing cues in electric hearing

Background. An increasing number of children and adults who are deaf are receiving cochlear implants in both ears (bilateral CIs or BiCIs), promoting the possibility of access to binaural cues. However, their effectiveness remains limited, as they do not adequately restore key acoustic cues for sound localization, particularly interaural time differences (ITDs) at low frequencies. The cochlea, the auditory sensory organ, typically transmits information for encoding ITDs more effectively at the apical region, which is specifically "tuned" to low frequencies. However, sensitivity to electrically-stimulated ITDs does not necessarily follow the non-implanted anatomy. We hypothesized that effective restoration of robust ITD perception through electrical stimulation with BiCIs depends on targeting cochlear locations that transmit information most effectively.

Methods. We created a personalized sound-coding strategy that delivered ITDs to each participant's single "best" cochlear location. We then evaluated the spatial hearing of 14 BiCI listeners using this "Best" strategy and compared it with three control strategies.

Results. Here, we show an improvement in perception of ITDs with a tone stimulus with the "Best" strategy. However, this benefit does not seem to translate to speech stimuli.

Conclusions. This suggests that restoration of ITD sensitivity requires targeting more than one good cochlear location for redundancy when it comes to more complex sounds such as speech.